One thing I've used in the past for this sort of thing are Scheme functions, specifically file-exists? .
https://www.gnu.org/software/mit-scheme/documentation/mit-scheme-ref/File-Manipulation.html
Another solution is to use some sort of top-level compilation script in bash or python, which is how i manage style sheets for large scores (I generate temporary ly files on the fly).
-------- Original message --------
From: Noeck <address@hidden>
Date: 11/19/16 11:50 AM (GMT+02:00)
To: lilypond-user <address@hidden>
Subject: try except in lilypond
Hi,